The human skeleton is composed of 206 individual bones that perform a variety of important functions, including support, movement, protection, storage of minerals, and formation of blood cells. These bones can be grouped into two categories, the axial skeleton and the appendicular skeleton. The axial skeleton consists of 80 bones that make up the body's center of gravity, and the appendicular skeleton consists of 126 bones that make up the body's appendages. The axial skeleton includes the skull, vertebral column, ribs, and sternum, among others, and the appendicular skeleton includes the long bones of the upper and lower limbs, and the clavicles and other bones that attach these long bones to the axial skeleton, among others.
To ensure that the skeleton retains its ability to perform its important functions, and to reduce pain and disfigurement, fractured bones should be repaired promptly and properly. Typically, fractured bones are treated using fixation devices, which reinforce the fractured bones and keep them aligned during healing. Fixation devices may take a variety of forms, including casts for external fixation and bone plates for internal fixation, among others. Casts are minimally invasive, allowing reduction and fixation of simple fractures from outside the body. In contrast, bone plates are internal devices that mount directly to bone to span a fracture.
Trauma to the torso may result in fracture of one or more ribs. Frequently, a simple rib fracture is nondisplaced, so that reduction and/or internal fixation of the fracture may not be required. However, in cases of more severe trauma to the chest, a single rib may be fractured more severely and/or multiple rib fractures may occur. With multiple rib fractures, a section of the thoracic wall may become detached from the rest of the chest wall, a condition known to medical practitioners as “flail chest”. A flail chest condition often results in paradoxical motion of the injured area, in which the freely floating thoracic section is drawn in during inspiration, and pushed out during expiration. This condition may result in severe respiratory distress, possibly requiring the patient to be sedated and/or intubated during early stages of healing. Fixing single or multiple rib fractures internally may alleviate paradoxical motion, reduce pain, and/or help to prevent secondary injuries.
Internal fixation of a rib fracture may be accomplished using a bone plate to span the fracture. A bone plate suitable for treating fractured ribs may be custom-contoured (i.e., bent) by a surgeon to conform to a region of a rib spanning a fracture, and then fastened to the rib on both sides of the fracture. The plate thus fixes the rib to permit healing. The plate may be fastened to the fractured rib using fasteners, such as bone screws, wires, and/or suture material, among others. Alternatively, a bone plate may be used that has prongs disposed along its length. The prongs may be crimped so that they grasp the rib to fasten the bone plate to the rib.
Each of these plating techniques may have disadvantages for rib fixation. For example, these techniques may not sufficiently stabilize the rib to provide adequate flexural and torsional support for the rib at the fracture site. Bone screws may not achieve adequate purchase in ribs to stabilize a bone plate because ribs are relatively thin and their bone density is low. Wires, suture material, and/or prongs also may not offer sufficient bone plate stabilization because they are not rigid enough. Each of these plating techniques thus may permit movement at the fracture with each breath, causing substantial pain and compromising the healing process. Furthermore, wires, suture material, and/or prongs may press on and damage a neurovascular bundle disposed on the inferior surface of ribs, if these fasteners are placed over this bundle during bone plate installation. Placement of these fasteners between the neurovascular bundle and bone still may damage the bundle and generally increases the time in surgery.